In the technique of the present invention, certain devices are employed of the types disclosed in various of my prior applications and patents above referred to. For example, various of the above applications and patents disclose heat exchangers embodying tube-in-tube units providing heat exchange passages within the inner tube and also in the annular space between the two tubes of each unit, one of the fluids involved in the heat exchange being passed through the inner tubes of each unit, and the other fluid being passed in the opposite direction through the annular space between the two tubes of each unit. In addition, various of the above applications and patents disclose a combustion chamber disposed within a heat exchanger and arranged to deliver the products of combustion to certain of the flow passages through the tube-in-tube units in order to provide for heat exchange to another fluid in other passages of the tube-in-tube units.
The prior applications and patents also disclose the arrangement of the heat exchanger to provide for cooling of combustion gases to a point below the dew point, in order to utilize the latent heat of evaporation of the moisture present in the combustion gases. Provision is also made in certain of the prior applications and patents for the use of elements lying within the heat transfer passages for the purpose of developing turbulence in the flow and thereby increasing the efficiency of heat exchange through the tube walls of the tube-in-tube units. Certain of the prior applications referred to also disclose heat exchange devices in which heat exchange elements subjected to acidic condensate are treated with special types of coatings, in order to resist the corrosive influence of such acidic condensate.
The present application is concerned with certain techniques and systems adapted for use in the handling of liquid cargo, especially viscous liquids, in transit or storage; and the present invention is particularly concerned with the use of certain of the features referred to in the preceding paragraphs in association with certain other features making up a system of exceptional efficiency, both from the standpoint of utilization of the energy available in fuels, and also from the standpoint of simplification of equipment while providing increased versatility with respect to the functions performed by the equipment. The technique of the present invention is particularly adapted to the handling of viscous liquids and especially in the barge handling of residual oils, such as #6 oil and also in the handling of other viscous materials, such as asphalt, molasses, etc.; and in view of this, the invention is herein described and illustrated in association with an oil barge, but it is to be understood that various features of the invention are also applicable to the handling of other cargo liquids on a vessel or other transport and/or storage facility. Certain features of the invention are effectively usable even with at least some nonviscous liquids, such as water and certain liquids used in solar energy systems.
In considering the invention as applied to a barge adapted for transport of oil, it is pointed out that in a typical #6 oil barge, an engine is commonly provided, usually a diesel engine, operating from a tank or source of diesel fuel, the engine serving to drive a pump which is utilized for the purpose of delivering the oil from the barge compartments or tanks at the destination of the barge. When the barge is loaded with oil, for instance #5 or #6 fuel oils, the oil is ordinarily pumped into the barge at a temperature in a range from about 125.degree. to 150.degree. F., at which temperature the oil is in a fluid state providing for efficient pumping. In the case of other viscous materials, certain other temperatures may desirably be observed in order to provide the desired fluidity for efficient pumping. For example, in the case of asphalt, the temperature would be of the order of 350.degree. F.
If the temperature of the viscous oil or other liquid is permitted to drop substantially, the pumping becomes difficult, inefficient and even impossible. For example, in the case of a typical relatively high viscosity #6 oil, if the temperature drops below about 115.degree. F., it becomes impractical to deliver the oil from the barge. In the handling of the oil, such drop in temperature has been encountered on many occasions merely as a result of encountering a cold front or because of travel of the barge from a loading area to a destination at which the atmospheric temperature is much lower than that at the starting point, for instance, from 20.degree. to 60.degree. F. lower. In many cases where this has occurred, it has become necessary for the barge to be removed from service, and even beached for a number of months, until seasonal weather change raises the average ambient temperature to a value which will again warm up the cargo to the point where it becomes possible to pump the oil from the compartments or tanks of the barge.
Certain attempts have been made to overcome some of the difficulties above referred to, including the construction of barges having extensive and expensive networks of piping within the tanks or compartments, in order to provide for the circulation of a heat transfer liquid through the pipes in the tanks and thus effect warming of the oil or other viscous liquid being transported. This prior type of system is subject to many disadvantages, including inefficiency in the use of the fuel used to operate the system, the cost of the equipment required, as well as the cost of installation, and also the fact that such prior technique is not economically adaptable to retrofitting of existing barges.
In connection with still another aspect of the present invention, it is first noted that in various oil-carrying barges, especially barges for residual type oils, the exposed connections or flow lines (commonly six or eight-inch i.d. piping) are enclosed in insulating jackets. In addition, it is also known to provide "tracers" associated with the exposed and insulated flow lines, the "tracers" comprising heat exchange tubes, for instance, a tube of about two-inches i.d., through which steam is passed, in order to effect heat transfer to the oil in the exposed flow lines, and thereby aid in preventing large increase in viscosity, such as would interfere with pumping of the oil. In a typical installation, such "tracers" are arranged in a loop, one end of the loop being used for input of the steam, and the other or return end of the loop being used for discharge; and the loop is ordinarily of sufficient length to provide for condensation of the steam at or close to the discharge end of the loop. In such a tracer system, a special source of steam was commonly provided and this, of course, increased original and installation costs of the barge.
One of the principal objects of the present invention is to overcome various problems and disadvantages such as those referred to above.
This general objective is accomplished according to the present invention by the employment of a technique including both equipment and method by which provision is made for maintaining the temperature of the residual oil (or other viscous liquid) in the compartments or tanks at a temperature providing the fluidity necessary for efficient pumping; and this is accomplished by employing one or more and preferably a multiple combination of unique features, including the following:
(a) Provision for transferring heat from the exhaust gases of the pump driving engine to the oil in the tanks; and preferably, this is achieved by employing the pump (ordinarily provided on the barge for delivery of the oil at the destination) in an alternative mode of operation effecting return circulation of the oil from the tanks through a heat exchanger in which the heat of the products of combustion of the engine is transferred to the oil. PA1 (b) The delivery of the products of combustion from the engine into a secondary combustion chamber with further addition of fuel so that the oxygen present in the engine exhaust is used in a secondary combustion, the secondary combustion products being utilized for additional heat transfer to the oil being carried in the tanks of the barge. PA1 (c) Utilization of the heat radiated from the cooling system of the engine to effect further heat transfer to the oil being carried in the tanks of the barge. PA1 (d) Provision is also made according to the present invention for the use of the heat of the secondary combustion not only to effect indirect heat transfer to the cargo carried in the compartments or tanks, but also to supply steam for tracers of the kind above referred to.
Additional efficiencies are effected in the technique of the present invention in a number of other respects, which will be explained more fully hereinafter following description of a typical installation according to the present invention.
In accordance with still another aspect of the invention, provision is made for delivery of the products of combustion from the secondary combustion chamber of the heat exchanger (in which the unused oxygen remaining in the engine exhaust is used in combustion of additional fuel) into the upper regions of the cargo compartments on the barge. The secondary combustion products represent an inert gas mixture which can thus be utilized to displace the air in the upper portions of the compartments, thereby virtually eliminating the dangers of fire or explosion.